Axial piston pump having a control device for varying the delivery



Oct. 6, 1964 T. MULLER 3,151,569

AXIM.y PIsIoNIEuuE HAVING A CONTROL nEvIcE Foa vVEREINE THE DELIVERYFiled Oct. 16, 1961 2 Sheets-Sheet 1 Fig. 1

y Y Z Oct. 6, 1964 T. MULLER 3,151,5694

AXIAI. PIsIoN PUMP HAVING A CONTROL DEVICE Foa VARYING THE DELIVERYFiled OCT.. 16, 1961 2 Sheets-Sheet 2 l t 97 9083 50 53 I 84 a7 88 51 s255 y l V i i l i l l, r n

United States Patent Ofice 3,151,569 AXIAL PISTGN PUMP HAVING A CONTROLDEVCE EGR VARYING THE DELIVERY Theodor Mller, Winterthur, Switzerland,assigner to Schweizerische Lokomotivund Maschinenfabrik, Winterthur,Switzerland Filed Get. 16, 1961, Ser. No. 145,145 Claims priority,application Switzerland, Get. 19, 1960, 11,723/60 12 Claims. (Cl.193-173) This invention relates to axial piston pumps of the type havinga control device for varying the delivery by restricting the ductsleading to the cylinder chambers.

In a known axial reciprocating pump of the swash plate type, a reductionof the rate of delivery is obtained by axial movements of the entiresystem consisting of the swash plate and the operating piston set in thedirection of the delivery stroke, for example by means of a mechanicaldevice.

It is an object of the invention to simplify the control system and tofacilitate the automatic control or" such pumps, as well as to obtain ashorter overall length of the pump unit. According to the invention, anaxial piston pump of the specified type comprises a control slide valveprovided in the pump housing and having ports which are associated withat least some of the cylinder chambers and communicate with the suctionspace of the pump, the position of said ports being adjustablerelatively to admission ducts leading to the cylinder chambers, so thatthe sectional area of ow provided for the admission of the liquid to thecylinder chambers will be variable.

The present invention will now be described in more detail withreference to the accompanying drawings illustrating, by way or example,two preferred embodiments of the invention, and in which:

FIGURE l is an axial section through a piston pump of a rst embodimentof the invention.

FIGURE 2 is a cross-section through the control slide along the lineIl-Il of FIGURE l,

FIGURE 3 represents a developed view of the inlets of the control ductsin dillerent relative control positions,

FIGURE 4 is a fragmentary axial section through a piston pump of thesecond embodiment,

FIGURE 5 is a transverse section along the line V-V of FIGURE 4,

FIGURE 6 shows a detail pertaining to the second embodiment, drawn to alarger scale, and

FIGURE 7 is a modification of the rst embodiment of the invention.

FIGURES l to 3 of the drawing illustrate an application of the inventionto that type or" pump in which a plurality of plungers are circularlyspaced around the axis of rotation of the pump driving shaft and areoperated by a swash plate of constant inclination. Said plungers,moreover, are subdivided into two groups of plungers having dilerentdiameter. With this subdivision of the plungers and cylinders it isknown that by cutting out the large diameter cylinders at higherdelivery pressure, it is possible to obtain a considerable increase ofthe delivery ratio at minimum and at maximum delivery pressure, whilethe load applied on the axial thrust bearings of the swash plate at e.g`400 lig/cm.2 operating pressure is approximately equal to that at lowoperating pressure of e.g. 40 lig/cm?. g

Within the pump housing 1 the drive shaft 2 is mounted in ball bearings3 and 4. The swash plate 5 is rigidly ixed to the shaft 2 for rotationwith the shaft. A plurality, eg. ten bores 6 and 7 extend parallel tothe drive shaft in circularly spaced arrangement in the actual cylinderblock part of the housing 1. The bores serve aS g 3,151,569 PatentedOct. V, 1964 cylinders for the pump plungers. There are ve bores 6 oflarger diameter d1 and iive bores 7 of smaller diameter d2. The pumpplungers 8 and 9 are provided with conical heads 11 which are urgedagainst a disk 12 by means of springs 10. The disk 12 forms part of theswash plate and is rotatably supported on the swash plate body 5 by ballbearings 13 and 14.

Each of the ve large and the ve small cylinders 6 and 7 is connected bymeans of a control duct 18 and 19, respectively, to an interior space17. When a plunger is at top dead centre position, the ducts 18 and 19are opened by the bottom edge of the plunger through an amount equal toh. In the interior 17 of the housing the control slide 29 common to allcylinders is guided for axial movement, but maintained against rotationby a bolt 21 engaging an axial groove 22 of the slide 20. The controlslide has radial ports 23 and 24 which register with the control ducts1S, 19 in the position of the slide shown in FIGURE l.

FIGURE 3 shows in the section a the control ducts 18, 19 in thedevelopment of the inner surface of the interior space 17, and also thedevelopment of the outer surface of the slide 20 together with the ports23, 24 in the lowermost position of the slide, in which the bores 18 andports 23, or 19 and 24, respectively, are in register. The sections band c correspondingly illustrate the ports 23, 24 of the slide indifferent vertical positions, and also the control ducts 18, 19 ascircles, drawn in dash and dot lines. The operating liquid is suppliedto the interior space 17 by means of the radial bores 25 in the housing1 which pass between the cylinders 6, 7.

The slide Ztl is urged by a spring 27 against a control cylinder 28which is retained in the pump housing 1 by a snap ring 29. A step piston3) is movable within the control cylinder 28. The distance f between itscontrol edges 32 and 33 corresponds to the distance g provided betweencontrol edges 34 and 35 of transverse bores 36 and 37 of the controlcylinder 28.

The control of the delivery of the pump is as follows:

At low operating pressure the control piston and the control slide 20assume the lowermost position, as indicated in FIGURE 1. As shown insection a of FIGURE 3 and as pointed out above, in this position theducts 18, 19 communicating with the cylinders are in register with theports 23, 24 oi the slide 20, and the plungers deliver through thepressure valves 38 the maximum output into the pressure chamber 39. Whenthe operating pressure of the pump in the pressure chamber 39 reaches apredetermined valve, the control piston 30 is forced upwardly by the uidpressure and moves the control slide 2l) upwards against the action ofthe spring 27. The ports 23, 24 then arrive for instance in a positionwith respect to the control ducts 18, 19 as shown in the developed viewin section b of FIGURE 3. As will be readily understood, the admissionof liquid to the control ducts 18 only is now restricted owing to theupwardly displaced control edges 23a of the ports 23; accordingly thedelivery of the live large diameter plungers S is reduced. Theadmissionof liquid to the small diameter cylinders, however,approximately remains the same as in the lowermost position of the slide20, so that the delivery of liquid by the live small plungerssubstantially remains unchanged.

When the operating pressure of the pump in the pressure chamber 39 risesstill higher and the control piston 30 moves upwardly through thedistance k, so that the edge 32 of the piston 30 meets the edge 34 ofthe duct 36, then the annular space 40 in the control cylinder 28 is cutot trom its communication with the pressure chamber 39 of the pump, andpressure in this space is relieved through ducts 37, 37a and 37b. Thecontrol piston 30 now moves suddenly through the distance i to itsupper- "ports 24, and still are in full operation.

In a modification, thercontrol slide may be constructed so that thelarge plungers 8 only operate when 'the slide is in its uppermostposition. Instead of making the diameter of the one group of plungers 9smaller than the diameter of the plungers 8 of the other group, thediameter of 'both groups of plungers could also be the same.

When at still increasing operating pressure the output ofthe smalldiameter plunger also shall be reduced, this may |be obtained forexample, as shown in FIGURE 7, by providing a bore through the controlpiston 30 and Y inserting a piston 44 in this bore, the lower end of thepiston being subjected to `the pressure prevailing in the chamber 39.When the control piston 30 is in its uppermost position, the smallpiston 44 may continue to move upwards owing to the pressure in -thechamber 39, and the piston 44, in turn, causes the slide 20 to movefurther upwardly. The admission conditions to ythe small diameter'cylinders will then change either-by a restriction of the inlet ductsbythe upper edge 42 of the control slide 20, or by a restriction'of theadmission to the ducts 19 by the edges 43 at the lower endV of thegrooves 22 of the control slide. It 'is possible in ,this matter, byproviding some of the edges 43`at a lower level than the others, tostill operate certain of the small diameter plungers at full deliveryrate.` The piston 44 may also be constructed as ,step piston, of whichthe .thicker portion moves Within thethicker section of thepiston 30.

It is also possi-ble to adjust the position of the control slide, e.g.by manual actuation, when extending the piston 44 downwardly through acentral bore in the cover 45 of the pressure chamber, as indicated bydot and dash lines in FIGURE 7. It thus may beactuated from its portion-projecting outwardly of the coverv 45.V The slide Z0, however, mayfalsobe Voperated exclusively at will, when piston is omitted and only thepiston rod 44 leading to the slide will be provided..

' The ,pump shown in FIGURE 1 operates automatically y so that itsdelivery decreases with increasing pressure. The manner 'of decrease inYdelivery asV l'function of the pressure depends on the selection of thespring 27; ina modilication, foi-example, a plurality of springs couldbe provided which can be subjected to pressure at the usame time or oneafter another. s l s The'modication according to FIGURES 4 4tof@ alsorelates to an axial piston pump havingrcircularly arranged,

Y parallel plungers'which are driven from a Vswash'plate of YKconstantrinclination similar to FIGURE n l. 'For` this reasonthe lowersection of the pump only is shown in VYFIGUIUE .4, In this case,however, Vlhe jcontrols'lide'is not arranged in thefinteriorY of Ithehousing YVso as to be 'axially' movable, but is positioned outsidethereof and' Yformed asan annular slide'sSG which is angularly movableabout the axisro'f the pump. Y The liquid tobe delivered Ventersthrough'the intake sleeves 51 and passes through the admission valves 52and the ducts 53 tothe cylinder spaces 54. The intake sleeves 51 areurged againstrthe annular vwall of the slide valve j50 `by theA springs55 (see .Y

V.FIGURE '6),' whereby a reliable seal'is secured between the slideY andthe Vintake sleeves, since the o uterrsurface of Vthese sleeveshas theksame radius as the vinner'surfaceV of Vthe slideA 5,0.VV VSpring loadeddischarge valves 57 are prol vided for the deliveryofthe liquidato thepressure'chamber 56, The pressure liquid leaves the pumpthroughthe 'twodschargeopenings 58. f

For the control of the annular slide 56 the latter is connected forexample to yan automatic adjusting device, as shown in'FIGURE. 5. Thisdevice comprises an arm 6i) which is connected to a control piston 61.The pis- Iton is urged outwardly in a xed cylinder 62 by a spring 63bearing against 'the top of the cylinder 62. The pressure chamber ofthis cylinder is connected by means of a conduit 64 with the pressurechamber 56 of the pump. The annular slide 5t) is provided with admissionports 71, 75 and 79 which are larger in circumferential direction thanthe ports 72, 73, 74, 76, 77, 7S, S0, 81 and 82. Due to vthe differentsize of the ports in circumferential direction not all inlet sleeves 51are out out at the same time when the control valve is angularly movedin the direction of the arrow 65. In the position of the control valve50 shown in FIGURE 5, the smaller admission ports 72- 74, 76-78 andSil-82 have already been closed and the associated nine pistons v66 arerelieved. Then the ad-V mission through the control port 71 is justbeing closed, while the control ports 75 and 79 are still open. When theslide 50 owing to an increasing pressure is rotated still further inclockwise direction, the lport 75 will close and finally also the port79. -By means Vof the described arrangement of staggered admissioncontrol edges it is possible to allow the pump to operate atreduceddelivery Y against very high delivery pressure without requiring anlincrease in driving power.

Yof the pump housing as a further improvement in theV koperatlon of thepump. This device comprises a cylinder 83, a control piston 84 which isaxially movable within said cylinder but not rotatable, and a piston rod85 cooperating with a resetting spring 86. Each cylinder, whichcommunicates with one of the smaller admission ports in the slide 50, isconnected with the vinterior of the cylinder 83 by awduct 87and 88. Theduct 88 opens into the bottom end -of the pump cylinder. For eachV duct87, 88, the controlpiston 84.is provided with a small transverse bore 89and longitudinalbore 90. All bores 90 at' their top end open in theinner spaceV of the pump and are coveredwith a rubber membrane 91 whichVpermits the discharge of liquid from the'rbores 90 in upward directionbut prevents liquid lfrom entering into these bores.

This additional control device operates in therfollow- .ing manner: Whenthe delivery pressure has increased to a predeternnned amount situatedclose to the maximum value and at the same time the'annular slide 5G hasbeen automatically Vturned Vthrough such an angle that the smallercontrol ports 72-74, 76-78, 80-82 are already Y n the ducts 87. 'Incasethat'the lsuction valves 52, the in- 'takesle'eves 51 vor thepressure'valves '57 should not keep quite tight and for this reasonsmall amounts of delivered Y liquid should have penetrated to'theVcylinder spaces 54 during the suctionstroke of the pump, then thesesmall amounts of liquid will be discharged without. any pressure throughthe ducts and bores S7-9i). Y InY the cut-out cylindersV no pressureaction due to liquid entered therein canV be` formed and the pump Willheprotectedagainst impacts of liquid against the pistons ofthesecylinders.

The described device Vmay also'be applied to the typepoii` `fpumpconstruction shown in FIGURE 1. Y A As further modification ofY apistonpumpaccording' to` the invention, the` control slide may be usedfor variT A ably supplyingronly a portion of the pump cylinders WhileYthe remainingcylinders operatecontinuously un-1 i changed adjustment,or are controlled in any other manner for varying the delivery.

I claim:

l. A pump comprising a pump housing, a plurality of parallel pumpcylinders circularly arranged in said housing and divided into twogroups of cylinders, pump plungers reciprocable in said cylinders, arotatably mounted swash plate coacting with said pump plungers forreciprocating said plungers, said housing having uid admission ductsleading to each cylinder, a movable annular control sleeve having portsin the annular Wall thereof for controlling the supply of tluid throughsaid admission ducts, pressure responsive piston means to move saidannular control sleeve, each of said ports in said sleeve coacting withone of said fluid admission ducts whereby a movement of said controlsleeve causes the sectional area of ow between said ports and said lluidadmission ducts to vary, the ports of said control sleeve having closingedges which cooperate With the admission ducts leading to the cylindersof one of said groups being displaced with respect to the closing edgesof the ports leading to the cylinders of the other of said groups, sothat upon a movement of said control sleeve the admission ducts of oneof said groups of cylinders are closed and those of the other group areopen.

2. A pump comprising a pump housing, a plurality of parallel pumpcylinders circularly arranged in said housing and divided into twogroups of cylinders, pump plungers reciprocable in said cylinders, arotatably mounted swash plate coacting with said pump plungers forreciprocating said plungers, said housing having fluid admission ductsleading to each cylinder, a movable annular control sleeve having portsin the annular wall thereof for controlling the supply of duid throughsaid admission ducts, pressure responsive piston means to move saidannular control sleeve, each of said ports in said sleeve coacting withone of said uid admission ducts whereby movement of said control sleevecauses the sectional area of flow between said ports and said fluidadmission ducts to vary, the ports of said control sleeve having closingedges which cooperate with the admission ducts leading to the cylindersoi the first of said groups being displaced with respect to the closingedges of the ports leading to the cylinders of the second of saidgroups, the closing edges cooperating with the admission ducts leadingto the cylinders of the second group moreover being displaced withrespect to one another, so that upon a predetermined movement of saidcontrol sleeve the admission ducts of the rst of said groups ofcylinders are closed and those of the second group are open, while onfurther movement of said control sleeve the admission ducts of thecylinders of the second group will successively and gradually be closed.

3. A pump in accordance with claim 2, in which said control sleeve ismounted for axial displacement in said housing.

4. A pump in accordance with claim 2, in which said plungers andcylinders of one of said groups have a diameter differing from thediameter of the plungers and cylinders of the other of said cylindergroups.

5. A pump in accordance with claim 2, in which means are provided forthe pressure responsive piston means to respond to an increase ofdelivery pressure to move said annular control sleeve.

6. A pump in accordance with claim 2, in which said control sleeve isangularly movable and iixed against axial displacement, and in which theports in said sleeve coacting with the uid admission ducts leading tothe second group of cylinders are larger in circumferential direction,than the ports in said sleeve coacting with the iiuid admission ductsleading to the tirst group of cylinders.

7. A pump comprising a pump housing, a plurality of parallel pumpcylinders circularly arranged in said housing and divided into twogroups of cylinders, purnp plungers reciprocable in said cylinders, arotatably mounted swash plate coacting with said pump plungers forreciprocating said plungers, said housing having fluid admission ductsleading to each of said cylinders, an axially movable annular controlsleeve having ports in the annular wall thereof for controlling thesupply of iluid through said admission ducts, an axially movable steppiston to move said control sleeve, said step piston having one end ofrelatively greater diameter and one end of relatively smaller diameter,an annular groove upon said piston separating said ends, said piston endof greater diameter being directly exposed to the delivery pressure ofthe pump and the smaller piston end abutting against said controlsleeve, a supplementary duct connecting said annular groove under normaloperating conditions with the delivery pressure, said piston end ofgreater diameter, upon a predetermined axial stroke caused by increaseddelivery pressure, raising said control sleeve and closing saidsupplementary duct whereby the piston is subjected to full deliverypressure acting solely on said end of greater diameter to further raisesaid control sleeve.

8. A pump in accordance with claim 7, in which said step piston has acylinder provided with au abutment which limits an additional iinalstroke of the step piston after this latter has closed saidsupplementary duct, said piston in the final stroke position completelyclosing the control ducts of the large diameter plungers.

9. A pump in accordance with claim 2, in which said control sleeve isoperatively connected with a separate regulating device subjected to thedelivery pressure of the pump.

10. A pump in accordance with claim 2, in which said control sleeve hasan annular Wall provided with a plurality of admission ports, certain otsaid admission ports being larger in circumferential direction than theother ports, so that the closing edges of the larger ports becomeeffective in staggered relation with respect to those of the smallerports.

11. A pump in accordance with claim 2, having its cylinders at leastpartly provided with suction valves and said control sleeve is arrangedoutside of the cylinder and plunger assembly of the pump.

12. A pump in accordance with claim 11, in which said annular controlsleeve surrounds said suction valves for the admission or" liquid, andintake sleeves are provided between said control sleeve and said suctionvalves radially supported in said suction valves and resiliently bearagainst the inner surface of said control sleeve.

References Cited in the file of this patent UNITED STATES PATENTS1,913,003 Shai June 6, 1933 2,093,477 Parsons Sept. 21, 1937 2,268,000Treer Dec. 30, 1941 2,357,563 Truxell Sept. 5, 1944 2,448,347 Beeh Aug.31, 1948 2,518,619 Huber Aug. l5, 1950 2,684,630 Widmer et al. July 27,1954 2,940,396 Misulis June 14, 1960 FOREIGN PATENTS 585,128 Canada Oct.13, 1959 808,811 France Feb. 16, 1937 516,721 Great Britain Jan. 10,1940 516,764 Great Britain Ian. 10, 1940 346,434 Switzerland June 30,1960

1. A PUMP COMPRISING A PUMP HOUSING, A PLURALITY OF PARALLEL PUMPCYLINDERS CIRCULARLY ARRANGED IN SAID HOUSING AND DIVIDED INTO TWOGROUPS OF CYLINDERS, PUMP PLUNGERS RECIPROCABLE IN SAID CYLINDERS, AROTATABLY MOUNTED SWASH PLATE COACTING WITH SAID PUMP PLUNGERS FORRECIPROCATING SAID PLUNGERS, SAID HOUSING HAVING FLUID ADMISSION DUCTSLEADING TO EACH CYLINDER, A MOVABLE ANNULAR CONTROL SLEEVE HAVING PORTSIN THE ANNULAR WALL THEREOF FOR CONTROLLING THE SUPPLY OF FLUID THROUGHSAID ADMISSION DUCTS, PRESSURE RESPONSIVE PISTON MEANS TO MOVE SAIDANNULAR CONTROL SLEEVE, EACH OF SAID PORTS IN SAID SLEEVE COACTING WITHONE OF SAID FLUID ADMISSION DUCTS WHEREBY A MOVEMENT OF SAID CONTROLSLEEVE CAUSES THE SECTIONAL AREA OF FLOW BETWEEN SAID PORTS AND SAIDFLUID ADMISSION DUCTS TO VARY, THE PORTS OF SAID CONTROL SLEEVE HAVINGCLOSING EDGES WHICH COOPERATE WITH THE ADMISSION DUCTS LEADING TO THECYLINDERS OF ONE OF SAID GROUPS BEING DISPLACED WITH RESPECT TO THECLOSING EDGES OF THE PORTS LEADING TO THE CYLINDERS OF THE OTHER OF SAIDGROUPS, SO THAT UPON A MOVEMENT OF SAID CONTROL SLEEVE THE ADMISSIONDUCTS OF ONE OF SAID GROUPS OF CYLINDERS ARE CLOSED AND THOSE OF THEOTHER GROUP ARE OPEN.